1. Field of the Invention
The present invention relates to an amplifier with bias stabilizer circuit including a configuration for stabilizing bias current of the circuit.
2. Description of Related Art
Generally, an analog electronic circuit is required to keep an operating point of each circuit element continually for a stabilized operation even when the circuit is in a standby state in which no meaningful signal output is expected. For example, an amplifier unit is sometimes connected to a current bias circuit to keep an operating point of a transistor. Even in such a case, the circuit needs to satisfy other requirements, such as a reduction in circuit area or circuit volume, reduction in cost of manufacturing, and a reduction in power consumption and so on.
Note that, nowadays, the above-mentioned analog electronic circuit is sometimes mounted on an LSI (Large Scale Integrated circuit) which is composed of CMOSFETs (Complementary Metal Oxide Semiconductor Field Effect Transistors).
Japanese Unexamined Patent Application Publication No. 2-108311 (Hughes) discloses an operation amplifier having a bias current source using a Widlar current mirror circuit which is composed of MOSFETs (see FIG. 3 of Hughes). In a non-patent document (P. R. Gray, P. J. Hurst, S. H. Lewis and R. G. Meyer, “ANALYSIS AND DESIGN OF ANALOG INTEGRATED CIRCUITS Fourth Edition”, John Wiley & Sons, Inc., pp. 299-317, New York, 2001.), a Widlar current mirror circuit and a peaking current mirror circuit are explained with their characteristics as well as the circuit schematics. Further, it also explains an operation principle of a self bias circuit which is a combination of these current mirror circuits and a current mirror circuit having a linear characteristic.